Braille is a writing system that employs combinations of raised dots to identify characters in a written alphabet. The raised dots are arranged into cells. The number and arrangement of the raised dots in a cell identify a particular character. In most versions of braille, each cell may contain up to six dots, although other versions employ more dots per cell.
Traditionally, braille characters have been formed by embossing raised dots on a medium such as paper. The advance of technology has allowed for the creation of electromechanical systems that are adapted to create refreshable braille displays. Refreshable braille displays consist of electromechanical character cells each of which can raise or lower a combination of six rounded-tip dots. In many instances, the mechanism by which the dots are raised and lowered relies upon the piezo-electric effect of expanding and reducing a crystal. In a typical design, a crystal is mechanically connected to a pin such that expansion of the crystal causes the pin to rise and thereby be exposed as a dot in a representation of a braille character. Removing a voltage from a crystal causes the crystal to return to its normal state and size and thereby cause the corresponding pin to be withdrawn.